Autonomous temperature transmitters can wirelessly transmit data and information and the energy needed to supply the field device is available without a wire connection to a feed point. Radio network technology can be available for wireless communication, however, using an autonomous energy supply can be problematic for industrial requirements. In certain applications, batteries have been used to enable an autonomous energy supply. Batteries can be inefficient, however, as they require regular monitoring and the replacement of used batteries can be complicated and costly.
DE 10 2007 051 672 A1 and US 2010/0091816 disclose devices for supplying energy to measuring and transmitting devices which use the energy content of the medium whose temperature is to be measured. For example, the electrical energy required for the electronics can be produced by a thermoelectric generator (TEG) such as a thin-film TEG or micro TEG, from the temperature difference between the medium and the environment.
Known techniques for providing autonomous energy have limitations in industrial scale applications, such as those applications where the available installation space is limited and functional reliability must be ensured due to explosion hazards or in the presence of aggressive gases. In particular, modular clamping solutions, as described in WO 2008/042073 A2, are inadequately integrated in the actual measuring device or field instrument.
DE 10 2007 056 150 A1 discloses a sensor system that is fed by a thermoelectric transducer. The transducer produces an electrical voltage with the action of a temperature gradient. The sensor system includes a carrier element which has a heat-conducting core that thermally couples the sensor and the thermoelectric transducer to the process medium representing the measurement variable. The design of this testing apparatus does not meet the industry standards for measurement accuracy and response times in the industrial sector.